Carbon Dioxide Sensitivity in Panic Anxiety

Abstract

• One hypothesis that could account for the anxiogenic response to breathing air supplemented with carbon dioxide seen in panic anxiety patients is that panic patients might have abnormally high central medullary chemoreceptor sensitivity. Chemoreceptor sensitivity was assessed by using a rebreathing technique to measure the ventilatory response to CO₂ in 14 medication-free patients with agoraphobia and panic attacks and 23 healthy subjects. Ventilatory response to CO₂ was similar in patients and controls (mean±SEM, 1.58 ± 0.16 vs 1.58±0.14 L/min/mm Hg), suggesting that abnormal chemoreceptor sensitivity does not explain the behavioral sensitivity of panic patients to CO₂. Anxiety ratings Increased markedly during rebreathing both in patients and controls; anxiety increases were significantly greater in patients than In healthy subjects matched for age, sex, and rebreathing duration. Alprazolam treatment in eight patients markedly attenuated anxiety increases during rebreathing. Differences in anxiogenic sensitivity to CO₂ between patients and controls may be due to differences in the regulation of noradrenergic or other neuronal systems.